Primordial perturbations and non-Gaussianities in DBI and general multi-field inflation

Abstract

We study cosmological perturbations in general inflation models with multiple scalar fields and arbitrary kinetic terms, with special emphasis on the multi-field extension of Dirac-Born-Infeld (DBI) inflation. We compute the second-order action governing the dynamics of linear perturbations in the most general case. Specializing to DBI, we show that the adiabatic and entropy modes propagate with a {\it common} effective sound speed and are thus amplified at sound horizon crossing. In the small sound speed limit, we find that the amplitude of the entropy modes is much higher than that of the adiabatic modes. We also derive, in the general case, the third-order action which is useful for studying primordial non-Gaussianities generated during inflation. In the DBI case, we compute the dominant contributions to non-Gaussianities, which depend on both the adiabatic and entropy modes.

20 pages

References in corpus (6)

• String Cosmology: A Review
• Perturbations in generalized multi-field inflation
• Primordial fluctuations and non-Gaussianities in multi-field DBI inflation
• Phenomenology of D-Brane Inflation with General Speed of Sound
• Multifield DBI Inflation and Non-Gaussianities
• Inflation, quantum fluctuations and cosmological perturbations

Cited by in corpus (20)

• Signature of Primordial Non-Gaussianity on Matter Power Spectrum
• On the Issue of the ζSeries Convergence and Loop Corrections in the Generation of Observable Primordial Non-Gaussianity in Slow-Roll Inflation. Part I: the Bispectrum
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• On the full quantum trispectrum in multi-field DBI inflation
• Lorentz boost and non-Gaussianity in multi-field DBI-inflation
• Primordial Trispectrum from Entropy Perturbations in Multifield DBI Model
• N-flation from multiple DBI type actions
• Nonlinear perturbations of cosmological scalar fields with non-standard kinetic terms
• The Trispectrum in the Multi-brid Inflation
• Multi-field Inflation with a Random Potential
• Systematics of multi-field effects at the end of warped brane inflation
• Dirac Born Infeld (DBI) Cosmic Strings
• Multi-Field Inflation on the Landscape
• Warped Wilson Line DBI Inflation
• Inflation on an Open Racetrack
• Nonlinear superhorizon perturbations of non-canonical scalar field
• Codimension-2 brane inflation
• Crossing the cosmological constant barrier with kinetically interacting double quintessence
• On the four-dimensional effective theories in brane-worlds
• Early Universe: inflation and cosmological perturbations